Direct digitization of ultra-wideband (UWB) noise signals using frequency band folding

Frequency spectrum responses of targets are of importance in UWB radar for target identification and recognition. As technology's digitization rate of analog sources increases, direct acquisition of wider bandwidths is becoming possible. Through conversion to the frequency domain, wider bandwidth spectral responses for targets can be produced. However, to directly digitize higher frequencies with UWB signals directly (i.e., = 4 GHz), the technology is somewhat limited. This paper will present a technique which utilizes both hardware and software to produce a lower bandwidth signal (e.g., 1.5 GHz), which contains larger spectral bandwidth information (e.g., 6 GHz). The technique utilizes a double band folding methodology implemented in hardware, or software, to translate larger bandwidths into lower bandwidths for direct digitization. The generated lower bandwidth will have a unique spectral response containing the superimposed amplitudes of the larger bandwidth transmitted signal. This folded spectrum can then be used in applications such as target recognition and identification. Simulated and experimental results will be presented to evaluate the advantages and disadvantages of such an approach.